JP5625380B2 - Magnetoresistive memory element and magnetic random access memory - Google Patents

Description

  The present invention relates to a magnetoresistive memory element and a magnetic random access memory (MRAM).

  MRAM is a promising nonvolatile memory from the viewpoint of high integration and high-speed operation. In the MRAM, a magnetoresistive element exhibiting a “magnetoresistance effect” such as a TMR (Tunnel MagnetoResistance) effect is used. For example, a magnetic tunnel junction (MTJ) in which a tunnel barrier layer is sandwiched between two ferromagnetic layers is formed in the magnetoresistive element. The two ferromagnetic layers are composed of a pinned layer (magnetization pinned layer) whose magnetization direction is fixed and a free layer (magnetization free layer) whose magnetization direction can be reversed (see Non-Patent Document 1). ).

  The resistance value (R + ΔR) of the MTJ when the magnetization directions of the pinned layer and the free layer are “anti-parallel” is larger than the resistance value (R) when they are “parallel” due to the magnetoresistance effect. It is known. The MRAM uses the magnetoresistive element having the MTJ as a memory cell, and stores data in a nonvolatile manner by utilizing the change in the resistance value. Data is written to the memory cell by reversing the magnetization direction of the free layer.

  Conventionally, an asteroid method is known as a method of writing data to the MRAM (see Non-Patent Document 2). FIG. 1 is a perspective view showing an example in which TMR is used as a storage element of a nonvolatile memory. In this example, a pair of intersecting wires B and D are installed above and below the TMR 505 arranged in an array. The free layer of the TMR 505 is connected to the upper wiring 506. The antiferromagnetic material layer of the TMR 505 is connected to the drain of the transistor 508 formed in the lower layer through the third wiring 507. By flowing current through the two wirings B and D, a synthetic magnetic field is generated near the intersection, and the magnetization direction of the free layer is set according to the direction of the current. Thereby, the resistance value of TMR505 can be changed. Data is read by turning on the transistor 508 connected to the TMR 505 to be read by the wiring W, applying a voltage to the TMR 505 from the wiring B, and evaluating the resistance value of the TMR with the flowing current. According to the asteroid method, the reversal magnetic field necessary for reversing the magnetization of the free layer increases in inverse proportion to the memory cell size. That is, as the memory cell is miniaturized, the write current tends to increase.

  As a write method that can suppress an increase in write current due to miniaturization, a “spin injection method (see, for example, Non-Patent Document 3)” has been proposed. According to the spin transfer method, a spin-polarized current is injected into a ferromagnetic conductor, and a direct interaction between the spin of a conduction electron carrying the current and the magnetic moment of the conductor is performed. Magnetization is reversed (hereinafter referred to as “Spin Transfer Magnetization Switching”). An outline of the spin injection magnetization reversal will be described with reference to FIG.

  FIG. 2 is a cross-sectional view showing a method of writing a magnetoresistive element using the spin transfer magnetization reversal method. The magnetoresistive element includes a free layer 601, a pinned layer 603, and a tunnel barrier layer 602. The tunnel barrier layer 602 is a nonmagnetic layer sandwiched between the free layer 601 and the pinned layer 603. Here, the pinned layer 603 whose magnetization direction is fixed is formed to be thicker than the free layer 601, and plays a role as a mechanism (spin filter) for creating a spin-polarized current. The state where the magnetization directions of the free layer 601 and the pinned layer 603 are parallel is associated with data “0”, and the state where they are antiparallel is associated with data “1”.

  The spin injection magnetization reversal shown in FIG. 2 is realized by a CPP (Current Perpendicular to Plane) method, and a write current is injected perpendicularly to the film surface. Specifically, current flows from the pinned layer 603 to the free layer 601 at the time of transition from data “0” to data “1”. In this case, electrons having the same spin state as the pinned layer 603 serving as a spin filter move from the free layer 601 to the pinned layer 603. Then, the magnetization of the free layer 601 is reversed by a spin transfer (spin angular momentum transfer) effect. On the other hand, at the time of transition from data “1” to data “0”, the direction of the current is reversed, and the current flows from the free layer 601 to the pinned layer 603. In this case, electrons having the same spin state as the pinned layer 603 serving as a spin filter move from the pinned layer 603 to the free layer 601. Due to the spin transfer effect, the magnetization of the free layer 601 is reversed. Thus, in spin injection magnetization reversal, data is written by the movement of spin electrons. The direction of magnetization of the free layer 601 can be defined by the direction of the spin-polarized current injected perpendicular to the film surface.

R. Scheuerlein et al. , “A 10 ns Read and Write Non-Volatile Memory Array Usage a Magnetic Tunnel Junction and FET Switch in PIECE CIT TECH NIT ETF 128-129. M.M. Durlam et al. , “Nonvolatile RAM based on Magnetic Tunnel Junction Elements”, 2000 IEEE International Solid-State Circuits Conference, DIGEST OF TECHNIC PAPER. 130-131. Yamami and Suzuki, Research Trends in Spin Transfer Magnetizing Switching, Journal of Japan Society of Applied Magnetics, Vol. 28, no. 9, 2004.

  The above-described spin injection magnetization reversal method can be written with a lower current than the asteroid method. However, since a write current is supplied to the tunnel barrier layer 602, there is a problem that the tunnel barrier film is easily deteriorated and it is difficult to ensure reliability.

  Accordingly, an object of the present invention is to provide a magnetoresistive memory element and a magnetic random access memory with high reliability while reducing a write current.

  Hereinafter, means for solving the problem will be described using the numbers and symbols used in the embodiments for carrying out the invention. These numbers and symbols are added with parentheses in order to clarify the correspondence between the description of the claims and the mode for carrying out the invention. However, these numbers and symbols should not be used for interpreting the technical scope of the invention described in the claims.

  In order to solve the above problems, a magnetoresistive memory element of the present invention includes a read structure and a write structure provided in the vicinity of the read structure. The readout structure includes a first free layer whose magnetization direction is changed, a magnetization fixed layer whose magnetization direction is fixed, and a tunnel insulating layer provided between the first free layer and the magnetization fixed layer. . The write structure includes a second free layer whose magnetization direction changes. The second free layer is provided on the upper surface of the film of the second free layer and is provided on the lower surface of the film with the first magnetization fixed region in which the magnetization is fixed in the first direction, and the magnetization direction in the second direction. And a second magnetization fixed region fixed. A domain wall exists in the film surface direction of the film. The first free layer and the second free layer are magnetostatically coupled.

  The magnetic random access memory according to the present invention includes a plurality of magnetoresistive storage elements and a peripheral circuit for driving the plurality of magnetoresistive storage elements. Each of the plurality of magnetoresistive memory elements is the magnetoresistive memory element described in the above paragraph.

  According to the present invention, it is possible to provide a highly reliable magnetoresistive memory element and magnetic random access memory while reducing a write current.

FIG. 1 is a perspective view showing an example in which a magnetoresistive element is used as a storage element of a nonvolatile memory. FIG. 2 is a cross-sectional view showing a method of writing a magnetoresistive element using the spin transfer magnetization reversal method. FIG. 3 is a cross-sectional view showing the configuration of the main part of the magnetoresistive memory element according to the first embodiment of the present invention. FIG. 4 is a schematic circuit diagram showing an example of the configuration of the MRAM according to the embodiment of the present invention. FIG. 5 is a cross-sectional view showing the configuration of the main part of the magnetoresistive memory element according to the second embodiment of the present invention. FIG. 6 is a schematic circuit diagram showing an example of the configuration of the MRAM according to the second embodiment of the present invention. FIG. 7 is a cross-sectional view showing the configuration of the magnetoresistive memory element according to the first embodiment of the present invention. FIG. 8A is a schematic plan view showing a configuration example of the magnetoresistive memory element according to the first example of the present invention. FIG. 8B is a schematic plan view showing a configuration example of the magnetoresistive memory element according to the first example of the present invention. FIG. 8C is a schematic plan view showing a configuration example of the magnetoresistive memory element according to the first example of the present invention. FIG. 9A is a schematic cross-sectional view showing another example of the writing structure according to the first embodiment of the present invention. FIG. 9B is a schematic cross-sectional view showing another example of the writing structure according to the first embodiment of the present invention. FIG. 10A is a schematic cross-sectional view showing another example of the read structure according to the first embodiment of the present invention. FIG. 10B is a schematic cross-sectional view showing another example of the read structure according to the first embodiment of the present invention. FIG. 10C is a schematic cross-sectional view showing another example of the read structure according to the first embodiment of the present invention. FIG. 10D is a schematic cross-sectional view showing another example of the read structure according to the first embodiment of the present invention. FIG. 10E is a schematic cross-sectional view showing another example of the read structure according to the first example of the present invention. FIG. 11 is a cross-sectional view showing the configuration of the magnetoresistive memory element according to the second embodiment of the present invention.

  Embodiments of a magnetoresistive storage element and a magnetic random access memory according to the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
A magnetoresistive storage element and a magnetic random access memory according to a first embodiment of the present invention will be described. First, the configuration of the magnetoresistive memory element according to the first embodiment of the present invention will be described. FIG. 3 is a cross-sectional view showing the configuration of the main part of the magnetoresistive memory element according to the first embodiment of the present invention. The magnetic random access memory (magnetoresistance storage device) according to the present embodiment includes a plurality of magnetoresistance storage elements. Each magnetoresistive memory element includes a read structure 21 and a write structure 22, as shown in FIG. The read structure 21 and the write structure 22 are located in a direction (Z direction in the figure) perpendicular to the film-forming surface of the magnetic material.

  The read structure 21 has a first free layer 1, a tunnel insulating layer 2, and a magnetization fixed layer 3. The first free layer 1 is a magnetic layer whose magnetization state changes according to data. The tunnel insulating layer 2 is an insulating layer. The magnetization fixed layer 3 is a magnetic layer whose magnetization direction is fixed in one direction. A first electrode 5 and a second electrode 6 are electrically connected to the first free layer 1 and the magnetization fixed layer 3 of the reading structure 21, respectively.

  The writing structure 22 has the second free layer 4. The second free layer 4 is a magnetic layer whose internal magnetization state changes according to data. A third electrode 7 and a fourth electrode 8 are electrically connected to the upper surface and the lower surface of the film formation surface of the second free layer 4, respectively. The second free layer 4 has a first magnetization fixed region 9 and a second magnetization fixed region 10 on the upper surface and the lower surface, respectively. The magnetization directions of the first magnetization fixed region 9 and the second magnetization fixed region 10 are fixed so as to be substantially opposite to each other along the easy magnetization axis.

  The write structure 22 has a domain wall motion region 11 between the first magnetization fixed region 9 and the second magnetization fixed region 10. A domain wall exists between one of the first magnetization fixed region 9 and the second magnetization fixed region 10 and the domain wall movement region 11. The domain wall moves inside the domain wall moving region 11 to the first magnetization fixed region 9 side or the second magnetization fixed region 10 side by a write operation described later.

  The first magnetization fixed region 9, the second magnetization fixed region 10, and the domain wall motion region 11 may all be formed of the same material. Alternatively, at least one of the first magnetization fixed region 9, the second magnetization fixed region 10, and the domain wall motion region 11 may be formed of different materials.

  The second free layer 4 has a length in a direction perpendicular to the magnetic film deposition surface (Z direction in the figure) and a direction of the magnetic film deposition surface (X direction or Y in the figure). It is preferable that the length is longer than the length of the direction. This is because the first magnetization fixed region 9 and the second magnetization fixed region 10 having different magnetization directions can be easily formed on the upper surface and the lower surface of the second free layer 4.

  The first free layer 1 and the second free layer 4 are magnetostatically coupled (indicated by an arrow C1 in the figure), and when the magnetization direction of the second free layer 4 changes, the first free layer 1 The magnetization direction also changes to the corresponding direction.

  The magnetic material used for the first free layer 1 and the second free layer 4 can be a magnetic material having an easy axis in the film formation surface, a magnetic material having an easy axis perpendicular to the film formation surface, and combinations thereof. It is. Each of the magnetic bodies may be a laminated film of a plurality of magnetic bodies, or a laminated film of a plurality of magnetic bodies and a nonmagnetic body layer in which the upper and lower magnetic bodies are ferromagnetically coupled or antiferromagnetically coupled. It is also possible to control the anisotropic strength by laminating a magnetic material having an easy axis in the film formation surface and a magnetic material having an easy axis perpendicular to the film formation surface. The center of the read structure 21 and the center of the write structure 22 may coincide with each other with respect to the film surface direction. The read structure 21 and the write structure 22 may be stacked in the reverse order of FIG. The stacking order of the readout structures 21 may be the reverse of FIG.

  In FIG. 3, the read structure 21 and the write structure 22 are positioned in a direction perpendicular to the film-forming surface of the magnetic material (Z direction in the figure). However, if the first free layer 1 and the second free layer 4 can be magnetostatically coupled, the read structure 21 and the write structure 22 are somewhat different from each other in the XY plane direction from the position in the Z direction. The position may be shifted.

  Next, the write operation of the magnetoresistive memory element according to the first embodiment of the present invention will be described. Data is written by applying a voltage between the third electrode 7 and the fourth electrode 8 of the writing structure 22 and passing a current through the second free layer 4.

  When a current is supplied from the third electrode 7, electrons whose spin direction is biased in the magnetization fixed direction of the second magnetization fixed region 10 are changed from the second magnetization fixed region 10 to the domain wall motion region of the second free layer 4. 11 is injected. As a result, the domain wall resident in the second free layer 4 and extending in the film surface direction moves in the direction of the first magnetization fixed region 9 (in the + Z direction in the figure) perpendicular to the film surface. As a result, the magnetization direction of the domain wall motion region 11 of the second free layer 4 faces the magnetization direction of the second magnetization fixed region 10. That is, the magnetization direction of the second free layer 4 changes as a whole in the easy axis direction closer to the magnetization direction of the second magnetization fixed region 10.

  On the other hand, when a current is supplied from the fourth electrode 8, electrons whose spin direction is biased in the magnetization fixed direction of the first magnetization fixed region 9 are changed from the first magnetization fixed region 9 to the domain wall of the second free layer 4. It is injected into the moving area 11. As a result, the domain wall that is resident in the second free layer 4 and extends in the film surface direction moves in the direction of the second magnetization fixed region 10 (−Z direction in the drawing) perpendicular to the film surface. As a result, the magnetization direction of the domain wall motion region 11 of the second free layer 4 faces the magnetization direction of the first magnetization fixed region 9. That is, the magnetization direction of the second free layer 4 changes as a whole in the easy axis direction closer to the magnetization direction of the first magnetization fixed region 9.

  Thus, the magnetization direction of the second free layer 4 can be set by the direction of the write current. Thereby, data can be written in the magnetoresistive memory element. At this time, the magnetization direction of the first free layer 1 magnetostatically coupled to the second free layer 4 is also set by the change in the magnetization direction of the second free layer 4.

  Note that when a current is supplied from the third electrode 7 and there is a domain wall in the vicinity of the first magnetization fixed region 9 from the beginning, the domain wall movement hardly occurs. Similarly, when a current is supplied from the fourth electrode 8 and there is a domain wall in the vicinity of the second magnetization fixed region 10 from the beginning, the domain wall movement hardly occurs. That is, the same data can be overwritten.

  Next, a read operation of the magnetoresistive memory element according to the first embodiment of the present invention will be described. Data is read by evaluating a characteristic value having a correlation with the resistance of the read structure 21. The read structure 21 has a resistance value that varies depending on the relationship between the magnetization direction of the first free layer 1 and the magnetization direction of the magnetization fixed layer 3. Therefore, different resistance values are shown depending on the data. Therefore, for example, a constant current is passed between the first electrode 5 and the second electrode 6, and the data is discriminated by comparing the magnitude of the voltage applied at this time with the reference voltage prepared in advance ( Read).

  Next, an example of the configuration of the MRAM according to the first embodiment of the present invention will be described. FIG. 4 is a schematic circuit diagram showing an example of the configuration of the MRAM according to the first embodiment of the present invention. The MRAM 40 includes a memory cell array 41 and peripheral circuits. The peripheral circuit includes a bit line control circuit 57, a word line control circuit 60, a select circuit 62, a read line control circuit 64, a differential sense amplifier 65, and a reference potential application circuit 66. The memory cell array 41 includes a plurality of memory cells C (C11,...) Arranged in a matrix, a plurality of first word lines 58, a plurality of second word lines 59, and a plurality of leads extending in the X direction. The line 63 includes a plurality of first bit lines 55, a plurality of second bit lines 56, and a plurality of data lines 61 extending in the Y direction.

  The memory cell C (C11,...) Includes a magnetoresistive storage element having a write structure 50 (corresponding to the write structure 22 in FIG. 3) and a read structure 51 (corresponding to the read structure 21 in FIG. 3); 1 transistor 52, second transistor 53, and third transistor 54. One electrode of the writing structure 50 is connected to the first bit line 55 through the first transistor 52, and the other electrode is connected to the second bit line 56 through the second transistor 53. The first bit line 55 and the second bit line 56 are connected to a bit line control circuit 57. The gate of the first transistor 52 is connected to the first word line 58, and the gate of the second transistor 53 is connected to the second word line 59. The first word line 58 and the second word line 59 are each connected to the word line control circuit 60. One electrode of the read structure 51 is grounded, and the other electrode is connected to the data line 61 via the third transistor 54. The data line 61 is connected to the select circuit 62. The gate of the third transistor 54 is connected to the lead wire 63. The lead wire 63 is connected to the lead wire control circuit 64. The output of the select circuit 62 is connected to one input of the differential sense amplifier 65. The output of the reference potential applying circuit 66 is connected to the other input of the differential sense amplifier 65.

  In the write operation, first, the selection of the first bit line 55 and the second bit line 56 by the bit line control circuit 57 and the first word line 58 and the second word line 59 by the word line control circuit 60 are performed. The memory cell C (write structure 50) to be written is selected by the selection. Next, data is written to the write structure 50 of the selected memory cell C by applying a write current corresponding to the data direction by the bit line control circuit 57. However, the current path is the first bit line 55 -the first transistor 52 -the write structure 50 -the second transistor 53 -the second bit line 56.

  In the read operation, first, the memory cell C (read structure 51) to be read is selected by selecting the lead wire 63 by the lead wire control circuit 64 and selecting the data line 61 by the select circuit 62. Next, a read current is supplied to the read structure 51 of the selected memory cell C by the select circuit 62. Data is read by comparing the voltage generated on the data line 61 with the reference potential of the reference potential applying circuit 66 by the differential sense amplifier 65. However, the current path is data line 61-third transistor 54-read structure 51-ground.

  The MRAM is an example of a magnetoresistive storage device. A MARM (magnetoresistance memory device) is not limited to this example as long as it has a circuit configuration capable of the above-described write operation and read operation.

  For the reference potential output from the reference potential applying circuit 66, a set of reference cells having the same shape as the memory cell C is prepared in the memory array 41, and [0] and [1] are respectively written and the memory cell C is read out. The potential obtained by the same means (example: average value of [0] potential and [1] potential) may be used.

  In the configuration example of the present MRAM, the writing system circuit and the reading system circuit are separated from each other, so that each may be formed on a separate substrate and bonded together. Which part is assigned to each substrate, such as forming the grounded read structure 21 on one substrate and preparing and bonding the peripheral circuit, the write structure 22 and the third transistor 54 on the other substrate? Is optional.

  According to the present embodiment, since a writing method using domain wall motion is used, writing at a low current is possible, and further, since the tunnel insulating layer has a structure in which no writing current flows, deterioration of the tunnel insulating film due to writing. Therefore, a highly reliable MRAM (magnetoresistance memory device) can be obtained.

(Second Embodiment)
A magnetoresistive storage element and a magnetic random access memory according to a second embodiment of the present invention will be described. First, the configuration of the magnetoresistive memory element according to the second embodiment of the present invention will be described. FIG. 5 is a cross-sectional view showing the configuration of the main part of the magnetoresistive memory element according to the second embodiment of the present invention. The magnetoresistive memory device (magnetic random access memory) according to the present embodiment includes a plurality of magnetoresistive memory elements. As shown in FIG. 4, each magnetoresistive memory element includes a read structure 21 and a write structure 22. The read structure 21 and the write structure 22 are located in a direction (Z direction in the figure) perpendicular to the film-forming surface of the magnetic material.

  In the second embodiment, the magnetization fixed layer 3 of the read structure 21 and the first magnetization fixed region 9 of the write structure 22 use electrodes in common. And different. Thereby, the number of electrodes per one magnetoresistive memory element (one memory cell) can be reduced. As a result, the degree of freedom in designing the memory cell can be improved and the area can be reduced.

  Regarding the material type, laminated structure, write method, and read method of the magnetoresistive memory element, the first embodiment is the same as the first embodiment except that the magnetization fixed layer 3 and the first magnetization fixed region 9 use electrodes in common. Since it is the same as the form, the description thereof is omitted.

  Next, an example of the configuration of the MRAM according to the second embodiment of the present invention will be described. FIG. 6 is a schematic circuit diagram showing an example of the configuration of the MRAM according to the second embodiment of the present invention. The MRAM 40 includes a memory cell array 41 and peripheral circuits. The peripheral circuit includes a bit line control circuit 57, a word line control circuit 60, a select circuit 62, a read line control circuit 64, a differential sense amplifier 65, and a reference potential application circuit 66. The memory cell array 41 includes a plurality of memory cells C (C11,...) Arranged in a matrix, a plurality of first word lines 58, a plurality of second word lines 59, and a plurality of leads extending in the X direction. The line 63 includes a plurality of first bit lines 55 and a plurality of second bit lines 56 extending in the Y direction.

  In the second embodiment, the plurality of data lines 61 in the first embodiment are omitted, and the plurality of first bit lines 55 also have the function thereof. And different. As a result, the wiring layer per row of memory cells can be reduced. As a result, the degree of freedom in designing the memory cell array can be improved and the area can be reduced. This will be specifically described below.

  The memory cell C (C11,...) Includes a magnetoresistive storage element having a write structure 50 (corresponding to the write structure 22 in FIG. 5) and a read structure 51 (corresponding to the read structure 21 in FIG. 5), 1 transistor 52, second transistor 53, and third transistor 54. One electrode of the writing structure 50 is connected to the first bit line 55 via the first transistor 52 and to one electrode of the reading structure 51. The other electrode is connected to the second bit line 56 via the second transistor 53. One of the first bit lines 55 is connected to the bit line control circuit 57 and the other is connected to the select circuit 62. The second bit line 56 is connected to the bit line control circuit 57. The gate of the first transistor 52 is connected to the first word line 58, and the gate of the second transistor 53 is connected to the second word line 59. The first word line 58 and the second word line 59 are each connected to the word line control circuit 60. One electrode of the read structure 51 is connected to the first bit line 55 via the first transistor 52, and the other electrode is grounded via the third transistor 54. The gate of the third transistor 54 is connected to the lead wire 63. The lead wire 63 is connected to the lead wire control circuit 64. The output of the select circuit 62 is connected to one input of the differential sense amplifier 65. The output of the reference potential applying circuit 66 is connected to the other input of the differential sense amplifier 65.

  In the write operation, first, the selection of the first bit line 55 and the second bit line 56 by the bit line control circuit 57 and the first word line 58 and the second word line 59 by the word line control circuit 60 are performed. The memory cell C (write structure 50) to be written is selected by the selection. At this time, the lead wire control circuit 64 deselects all the lead wires 63 and turns off the third transistor 54. This prevents the write current from flowing from the read structure 51 to ground. Next, data is written to the write structure 50 of the selected memory cell C by applying a write current corresponding to the data direction by the bit line control circuit 57. However, the current path is the first bit line 55 -the first transistor 52 -the write structure 50 -the second transistor 53 -the second bit line 56.

  In the reading operation, first, the selection of the lead line 63 by the read line control circuit 64, the selection of the first word line 58 by the word line control circuit 60, and the first bit line by the bit line control circuit 57 and the selection circuit 62 are performed. The memory cell C (read structure 51) to be read is selected by selecting 55. Next, a read current is passed through the read structure 51 of the selected memory cell C by the bit line control circuit 57. Then, data is read by comparing the voltage generated on the first bit line 55 with the reference potential of the reference potential applying circuit 66 by the differential sense amplifier 65. However, the current path is first bit line 55 -first transistor 52 -readout structure 51 -third transistor 54 -ground.

Others are the same as those in the first embodiment.
The MRAM is an example of a magnetoresistive storage device. A MARM (magnetoresistance memory device) is not limited to this example as long as it has a circuit configuration capable of the above-described write operation and read operation.

  In this case, the same effect as that of the first embodiment can be obtained. Furthermore, according to the present embodiment, the number of electrodes can be reduced as compared with the first embodiment.

  Hereinafter, each of the above-described embodiments will be specifically described using examples.

(First embodiment)
FIG. 7 is a cross-sectional view showing the configuration of the magnetoresistive memory element according to the first embodiment of the present invention. FIG. 8 is a plan view showing the configuration of the magnetoresistive memory element according to the first embodiment of the present invention.

In this magnetoresistive memory element, a write structure 22 and a read structure 21 are vertically arranged in the vertical direction. The magnetoresistive memory element is provided on a semiconductor substrate (not shown) on which transistors, wirings, and the like are formed. A Cu wiring (Cu lower electrode) 72 having a Ta film 71 as a barrier film embedded in an SiO ₂ film 70 as an interlayer insulating film is provided below the writing structure 22. On the Cu wiring 72, as the write structure 22, a Ta film 73 having a film thickness of 5 nm as an underlayer, a PtMn film 74 having a film thickness of 20 nm as an antiferromagnetic material, and a film having a film thickness of 4 nm as a magnetic material under the pinned layer are formed. CoFe film 75, 0.8 nm thick Ru film 76, which is a conductor layer for antiferromagnetic coupling between pinned layers, 4 nm thick CoFe film 77, which is a pinned layer upper magnetic body, and free layer 4 thickness. A Co film 78 having a thickness of 50 nm, a PtMn film 79 having a thickness of 20 nm that is an antiferromagnetic material, and a Ta film 80 having a thickness of 50 nm that is a cap layer are laminated in this order. The writing structure 22 is embedded in the SiO ₂ film 81 that is an interlayer insulating film. On the upper side of the writing structure 22, a Cu wiring (Cu upper electrode) 85 having a Ta film 84 as a barrier film embedded in an SiN film 82 and an SiO ₂ film 83 as interlayer insulating films is provided.

  However, the PtMn film 74, which is an antiferromagnetic material, fixes at least the magnetization direction of the CoFe film 75 of the pinned layer lower layer magnetic material. The CoFe film 75 of the pinned layer lower magnetic material and the CoFe film 77 of the pinned layer upper magnetic material constitute a pinned layer antiferromagnetically coupled via the Ru film 76. In the pinned layer, the lower region of the Co film 78 as the free layer 4 is used as the second magnetization fixed region 10, and the magnetization direction is fixed. The antiferromagnetic PtMn film 79 uses the upper region of the Co film 78 as the free layer 4 as the first magnetization fixed region 9 and fixes the magnetization direction thereof.

  Further, the CoFe film 77 and the Co film 78 can be collectively regarded as the free layer 4. Furthermore, the pinned layer composed of the CoFe films 75 and 77 and the Ru film 76 and the Co film 78 can be regarded as the free layer 4 together.

On the Cu wiring 85, an SiO ₂ film 86 having a thickness of 400 nm and an SiN film 87 having a thickness of 20 nm, which are interlayer insulating films, are provided. A Cu wiring (Cu lower electrode) 90 having a Ta film 89 as a barrier film embedded in an SiO ₂ film 88 as an interlayer insulating film on the SiN film 87 is provided below the read structure 21. . On the Cu wiring 90, as a readout structure 21, a Ta film 91 with a film thickness of 5 nm as an underlayer, a PtMn film 92 with a film thickness of 20 nm as an antiferromagnetic material, and a film with a film thickness of 4 nm as a magnetic material under a pinned layer. CoFe film 93, Ru film 94 with a film thickness of 0.8 nm that is a conductor layer for antiferromagnetic coupling between pinned layers, CoFe film 95 with a film thickness of 4 nm that is a magnetic material on the pinned layer, and a film that is tunnel insulating layer 2 A 1 nm thick MgO film 96, a 3 nm thick NiFe film 97 as the first free layer 1, and a 50 nm thick Ta film 98 as a cap layer are laminated in this order. The read structure 21 is embedded in an SiO ₂ film 99 that is an interlayer insulating film. On the upper side of the readout structure 21, a Cu wiring (Cu upper electrode) 103 having a Ta film 102 as a barrier film embedded in an SiN film 100 and an SiO ₂ film 101 as interlayer insulating films is provided.

  However, the PtMn film 92 that is an antiferromagnetic material fixes at least the magnetization direction of the CoFe film 93 that is a pinned layer lower layer magnetic material. The CoFe film 93 of the pinned layer lower magnetic body and the CoFe film 95 of the pinned layer upper magnetic body constitute the magnetization fixed layer 3 that is antiferromagnetically coupled via the Ru film 94.

Next, a method for manufacturing the magnetoresistive memory element according to the first embodiment will be described with reference to FIG.
A Cu wiring (Cu lower electrode) 72 is formed on a part of the SiO ₂ film 70 which is an interlayer insulating film provided on a semiconductor substrate (not shown) on which transistors, wirings and the like are formed. And the upper part is planarized by the chemical mechanical polishing technique (Chemical Mechanical Polishing: hereinafter CMP). Thereafter, the Ta film 73 is 5 nm, the PtMn film 74 is 20 nm, the CoFe film 75 is 4 nm, the Ru film 76 is 0.8 nm, the CoFe film 77 is 4 nm, the Co film 78 is 50 nm, the PtMn film 79 is 20 nm, and the Ta film. Films 80 and 50 nm are formed by sputtering. Subsequently, the Ta film 80 is processed by a photolithography technique and a reactive ion etching technique (hereinafter referred to as RIE). After removing the resist by the ashing process, the PtMn film 79 to the Ta film 73 are processed into the shape of the writing structure 22 by the milling method using the Ta film 80 as a mask. Thereafter, an SiO ₂ film 81 having a thickness of 200 nm is formed on the entire surface by CVD, followed by planarization by CMP and exposing the Ta80 film.

Thereafter, an SiN film 82 is formed on the surface and an SiO ₂ film 83 is formed at 400 nm. Subsequently, a groove is formed in the SiO ₂ film 83 by photolithography and RIE, and the resist is removed by ashing. Next, the SiN film 82 in the trench is removed by RIE. Subsequently, after a Ta film 84 is formed on the entire surface, a Cu film 85 is grown by plating. Thereafter, the entire surface is subjected to CMP to form a Cu wiring 85 serving as an upper electrode of the write structure 22 only in the groove.

Thereafter, an SiO ₂ film 86 is formed on the surface at 400 nm, an SiN film 87 is formed at 20 nm, and an SiO ₂ film 88 is formed at 400 nm. Subsequently, a groove is formed in the SiO ₂ film 88 by photolithography and RIE, and a Cu wiring 90 that is a lower electrode of the readout structure 21 is formed by the same process as described above.

Next, on the entire surface, the Ta film 91 is 5 nm, the PtMn film 92 is 20 nm, the CoFe film 93 is 4 nm, the Ru film 94 is 0.8 nm, the CoFe film 95 is 4 nm, the MgO film 96 is 1 nm, the NiFe film 97 is 3 nm, Ta A film 98 is formed to a thickness of 50 nm by a sputtering method. Subsequently, the Ta film 98 is processed by photolithography and RIE. After removing the resist by the ashing process, the NiFe film 97 to the Ta film 91 are processed into the shape of the readout structure 21 by the milling method using the Ta film 98 as a mask. After that, an SiO ₂ film 99 is formed on the entire surface by 200 nm by the CVD method, and then planarized by CMP and the Ta film 98 is exposed. Then, a Cu wiring 103 serving as the upper electrode of the readout structure 21 is formed by the same process as described above.

  Thereafter, annealing is performed in a magnetic field in the in-plane direction of about 1T (Tesla) at 275 ° C. for 2 hours, and the antiferromagnetic layer (74, 92) for pinning the magnetization and the pinned layer whose magnetization direction is pinned ( 75/76/77, 93/94/95) are exchange-coupled to set the magnetization direction of those pinned layers (75/76/77, 93/94/95).

  The easy axis direction of the second free layer of the write structure 22, the easy axis direction of the first free layer of the read structure 21, and the pinned layers (75/76/77, 93/94/95) It is desirable to match the magnetization directions because the resistance difference of the read structure 21 due to data becomes the largest. Assume that the magnetization directions of these pinned layers (75/76/77, 93/94/95) are set as shown in FIG. The magnetization directions of the CoFe films 75 and 93 that are pinned layers in contact with the PtMn films 74 and 92 are fixed to the left in the drawing. At that time, the magnetization direction of the CoFe film 77 is fixed to the right in the figure by setting the Ru film 76 to a film thickness that antiferromagnetically couples the CoFe film 75 and the CoFe film 77. Further, since the upper surface portion of the Co film 78 is in contact with the PtMn film 79, the magnetization direction is fixed to the left in the figure. In this example, it can be seen that the CoFe film 77 and the Co film 78 form the second free layer of the write structure 22. As described above, the magnetization direction of the upper surface of the second free layer is fixed to the left in the drawing, and the magnetization direction of the lower surface is fixed to the right in the drawing, so that a domain wall is always formed in the second free layer.

  Next, the data write operation of the MRAM in FIG. 4 using the magnetoresistive memory element as a memory cell will be described. First, the first transistor 52 and the second transistor 53 are turned on via the first word line 58 and the second word line 59 of the memory cell in which data is written by the word line control circuit 60. Further, a voltage is applied between the first bit line and the second bit line of the memory cell to which data is written by the bit line control circuit 57, and the second free layer in the writing structure 50 (same as 22) A desired write current sufficient to move the domain wall, for example 1 mA, is passed. When a write current is passed from the Cu wiring 85 to the Cu wiring 72, electrons flow from the region of the magnetization fixed to the right of the CoFe film 77, and move the domain wall in the second free layer upward. As a result, the magnetization direction of the Co film 78 changes to the right. Further, when a write current is passed from the Cu wiring 72 to the Cu wiring 85, electrons flow from the region where the magnetization is fixed to the left on the upper surface of the Co film 78, and move down the domain wall in the second free layer. Let As a result, the magnetization direction of the Co film 78 changes to the left. The second free layer of the write structure 50 and the first free layer of the read structure 51 (same as 21) are magnetostatically coupled. Therefore, when the magnetization direction of the second free layer of the write structure 22 is set, the magnetization direction of the first free layer of the read structure 51 is also set. That is, the magnetization directions of the first free layer and the second free layer can be set according to the direction of the write current.

  Next, reading of data from the MRAM of FIG. 4 using the magnetoresistive memory element as a memory cell will be described. First, the third transistor 54 of the memory cell that performs reading via the lead wire 63 is turned on by the lead wire control circuit 64. Further, a read current, for example, 20 μA is applied to the data line 61 of the memory cell to be read from the select circuit 62. The read structure 21 has a resistance value of 10 kΩ or 20 kΩ depending on the written data. As a result, when the ON resistance of the selected third transistor 54 connected to the magnetization fixed layer (3) is 1 kΩ, the potential of the data line 61 shows 0.21V and 0.41V. Data can be discriminated by applying the potential of the data line 61 to the differential sense amplifier 65 and setting the reference potential Vref of the reference potential applying circuit 66 to 0.3V.

  8A to 8C are schematic plan views showing a configuration example of the magnetoresistive memory element according to the first example of the present invention. The first free layer of the read structure 21 (indicated by the NiFe film “97” in the figure) has a cross-sectional shape of the second free layer of the write structure 22 (in the figure, as shown in FIG. 8A). It is an ellipse having the same long side direction as that of the Co film “78”. However, since the first free layer (97) of the read structure 21 is magnetostatically coupled to the second free layer (78) of the write structure 22, it is necessary to change the magnetization direction easily. Therefore, the cross-sectional shape may be circular as shown in FIG. 8C. Alternatively, the first free layer (97) of the reading structure 21 may have a shape that is long in the direction orthogonal to the material anisotropic axis, for example, an ellipse, a rectangle, or a rhombus as shown in FIG. 8B. Since the second free layer (78) of the writing structure 22 has anisotropy in one direction, it may have a long shape in one direction as shown in FIGS. 8A and 8B. Further, in order to ensure anisotropy, the material anisotropy may be used to form a circular shape as shown in FIG. 8C.

  The magnetic material used as each free layer may be a magnetic single layer film or a magnetic layered film. Further, it may be a laminated film having a non-magnetic material and a magnetic material laminated on both surfaces thereof, and the magnetic material laminated on both surfaces is ferromagnetically coupled or antiferromagnetically coupled by the non-magnetic material. Further, the magnetic films laminated in the write structure 22 and the read structure 21 need not all have the same shape. For example, when the Co film 78 of the second free layer of the write structure 22 is a three-layer magnetic film, the central magnetic film may be enlarged. At this time, the smaller the area of the domain wall is, the more stable the domain wall is. Therefore, the domain wall can be prevented from staying in the central magnetic film.

  The centers of the write structure 22 and the read structure 21 may be shifted as shown in FIG. 8A, or may be coincident as shown in FIGS. 8B and 8C. The magnetic film of the second free layer (78) of the writing structure 21 may be a material having material anisotropy perpendicular to the film formation surface.

  The magnetization directions of the magnetization fixed regions formed on the upper surface and the lower surface of the second free layer of the write structure 22 need opposite components, and are preferably opposite to each other. As a method of forming the magnetization fixed region, for both the upper and lower magnetization fixed regions, a magnetic material laminated with an antiferromagnetic material and a magnetization direction fixed, and a magnetization fixed region are interposed via a non-magnetic material. Thus, an antiferromagnetic coupling or a ferromagnetic coupling method may be used. Specifically, the following examples can be considered.

  FIG. 9A is a schematic cross-sectional view showing another example of the writing structure according to the first embodiment of the present invention. In the example of FIG. 9A, the lower side is an antiferromagnetic material (CoFe film 75) laminated with an antiferromagnetic material (PtMn film 74) and an antiferromagnetic material via a nonmagnetic material (Ru film 76). A magnetization fixed region (CoFe film 77) that is magnetically coupled (or ferromagnetically coupled) is used. On the other hand, on the upper side, a magnetic body (CoFe film 107) laminated with an antiferromagnetic body (PtMn film 79) to fix the magnetization direction, and an antiferromagnetic coupling (or strong magnetic field) via a nonmagnetic body (Ru film 106). Magnetization fixed region using a magnetic material (CoFe film 105) that is magnetically coupled and antiferromagnetically coupled (or ferromagnetically coupled) via the magnetic material (CoFe film 105) and a non-magnetic material (Ru film 104) (CoFe film 103) is used. That is, one antiferromagnetic coupling is used on the lower side and two antiferromagnetic couplings are used on the upper side.

  As described above, the first and second magnetization fixed regions (CoFe film 103 and / or the upper part of the Co film 78) and the second magnetization fixed region (CoFe film 77) are changed by making the number of antiferromagnetic couplings on the upper and lower sides an odd number of times. And / or the magnetization direction of the lower part of the Co film 78 can be easily reversed. That is, in FIG. 9A, the magnetization direction of the magnetic CoFe films 75 and 107 in contact with the PtMn films 74 and 79 that are antiferromagnetic materials is leftward by annealing at a high temperature while applying a magnetic field in the left direction in the figure. However, the magnetization directions can be opposite to each other at the upper interface and the lower interface in the second free layer.

  As another method for forming the magnetization fixed region, the magnetic material and the magnetization fixed region may be antiferromagnetically coupled between the second free layer of the write structure 22 and the magnetization fixed magnetic material. A method of sandwiching a nonmagnetic material to be ferromagnetically coupled may be used. Specifically, the following examples can be considered.

  FIG. 9B is a schematic cross-sectional view showing another example of the writing structure according to the first embodiment of the present invention. This figure shows another method for forming a magnetization fixed region formed on the upper and lower surfaces of the second free layer. In the example of FIG. 9B, the lower side is between the second free layer (in this case, the Co film 78) and the magnetic substance for fixing magnetization (in this case, the CoFe film 75). ) And the lower magnetization fixed region are sandwiched by a non-magnetic material (in this case, the Ru film 76) for antiferromagnetic coupling or ferromagnetic coupling. On the other hand, on the upper side, between the second free layer (Co film 78) and the magnetization fixing magnetic substance (CoFe film 105), the magnetic substance (in this case, the CoFe film 105) and the upper magnetization fixed region Is sandwiched by a nonmagnetic material (in this case, the Ru film 104) for antiferromagnetic coupling or ferromagnetic coupling.

  The easy axis of the second free layer (such as the Co film 78) of the writing structure 22 may be a direction perpendicular to the film formation surface. The magnetization direction of the readout structure 21 (NiFe film 97 or the like) may also be a direction perpendicular to the film formation surface.

  When the first free layer of the read structure 21 uses magnetostatic coupling in the film surface direction, the read structure 21 having another structure can also be used. 10A to 10C are schematic cross-sectional views showing other examples of the read structure according to the first embodiment of the present invention. 10A shows that the magnetization direction of the magnetization fixed layer (CoPt film 113 / Ru film 94 / CoPt film 115) of the readout structure 21 is perpendicular to the film surface, and the easy axis of the first free layer (NiFe film 117) is the film. This is the case when it is perpendicular to the surface. The leakage magnetic field from the write structure 22 adjusts the magnetic material and thickness so that the intensity varies depending on the write data, so that the magnetization direction of the first free layer (NiFe film 117) of the read structure 21 depends on the data. Inclination and resistance change. The first anisotropy of the first free layer (NiFe film 117) of the readout structure 21 is desirably small. For this purpose, a material with small anisotropy is selected, or NiFe having in-plane anisotropy is formed thicker than the length in the direction of film formation, and the shape anisotropy has a small anisotropy in the vertical direction, It is preferable to use a film in which a perpendicular magnetization film and an in-plane magnetization film are laminated to have a weak anisotropy in the perpendicular direction.

  FIG. 10B shows that the first free layer (CoPt film 118) has perpendicular magnetic anisotropy, but the magnetization fixed layer (CoFe film 93 / Ru film 94 / CoFe film 95) has in-plane magnetic anisotropy. This is different from the case of FIG. 10A.

  FIG. 10C shows a case where the magnetization direction of both the magnetization fixed layer (CoFe film 93 / Ru film 94 / CoFe film 95) and the first free layer (NiFe film 119) is the film surface direction, but they are almost orthogonal to each other. It is. When the direction of the leakage magnetic field from the write structure 22 changes, the magnetization direction of the first free layer (NiFe film 119) also rotates, so that the resistance changes.

  When the first free layer of the read structure 21 uses magnetostatic coupling in a direction perpendicular to the film surface, the read structure 21 having another structure can also be used. 10D and 10E are schematic cross-sectional views showing other examples of the read structure according to the first embodiment of the present invention. FIG. 10D shows the case where the magnetization direction of the magnetization fixed layer (CoFe film 93 / Ru film 94 / CoFe film 95) is the film surface direction and the easy axis of the first free layer (NiFe film 120) is also the film surface direction. is there. The leakage magnetic field from the write structure 22 adjusts the magnetic material and the thickness so that the intensity varies depending on the write data, whereby the magnetization direction of the first free layer (NiFe film 120) is tilted according to the data and the resistance changes. To do.

  In FIG. 10E, the easy axis of the first free layer (NiFe film 120) is the film surface direction, but the magnetization direction of the magnetization fixed layer (CoPt film 113 / Ru film 94 / CoPt film 115) is perpendicular to the film surface. It differs from the case of FIG.

  In the first embodiment, data writing is performed by moving the domain wall resident in the free layer 4, so that writing with a low current can be realized. Further, since writing can be performed without flowing a write current through the tunnel insulating film (MgO film 96), deterioration of the tunnel insulating film can be suppressed.

(Second embodiment)
FIG. 11 is a cross-sectional view showing the configuration of the magnetoresistive memory element according to the second embodiment of the present invention.
In this magnetoresistive memory element, a write structure 22 and a read structure 21 are vertically arranged in the vertical direction. The magnetoresistive memory element is provided on a semiconductor substrate (not shown) on which transistors, wirings, and the like are formed. A Cu wiring (Cu lower electrode) 72 having a Ta film 71 as a barrier film embedded in an SiO ₂ film 70 as an interlayer insulating film is provided below the writing structure 22. On the Cu wiring 72, as a writing structure 22, a Ta film 73 having a film thickness of 5 nm as an underlayer, a PtMn film 74 having a film thickness of 20 nm as an antiferromagnet, and a film having a thickness of 2 nm as a magnetic material under the pinned layer are formed. The CoPt film 200, the Ru film 76 having a film thickness of 0.8 nm which is a conductor layer for antiferromagnetic coupling between the pinned layers, the CoPt film 201 having a film thickness of 2 nm which is a pinned layer upper magnetic body, and the film thickness 50 nm which is a free layer. A CoPt film 202, a second pinned layer lower layer CoPt film 203 having a film thickness of 2 nm, a second conductor layer antiferromagnetically coupling the pinned layers to each other, a 0.8 nm film thickness Ru film 204, CoPt film 205 with a film thickness of 4 nm as a pinned layer intermediate magnetic body, a Ru film 206 with a film thickness of 0.8 nm as a third conductor layer for antiferromagnetic coupling between the pinned layers, and a film as a magnetic material on the pinned layer. CoPt film 20 having a thickness of 2 nm , PtMn film 79 having a film thickness of 20nm is antiferromagnetic, Ta film 80 having a thickness of 50nm is capping layer are laminated in this order. The writing structure 22 is embedded in the SiO ₂ film 81 that is an interlayer insulating film. On the upper side of the writing structure 22, a Cu wiring (Cu upper electrode) 85 having a Ta film 84 as a barrier film embedded in an SiN film 82 and an SiO ₂ film 83 as interlayer insulating films is provided.

  However, the PtMn film 74 that is an antiferromagnetic material fixes at least the magnetization direction of the CoPt film 200 that is a pinned layer lower layer magnetic material. The CoPt film 200 of the pinned layer lower magnetic body and the CoFe film 201 of the pinned layer upper magnetic body constitute a pinned layer antiferromagnetically coupled via the Ru film 76. In the pinned layer, the lower region of the CoPt film 202 as the free layer 4 is used as the second magnetization fixed region 10, and the magnetization direction is fixed. The antiferromagnetic PtMn film 79 fixes at least the magnetization direction of the CoPt film 207 which is the pinned layer upper magnetic material. The CoPt film 207 that is the pinned layer upper layer magnetic material, the CoPt film 205 that is the pinned layer middle layer magnetic material, and the CoPt film 203 that is the second pinned layer lower layer magnetic material are anti-strength through the Ru film 206 and the Ru film 204. A magnetically coupled pinned layer is formed. In the pinned layer, the upper region of the CoPt film 202 as the free layer 4 is the first magnetization fixed region 9, and the magnetization direction is fixed.

  In addition, at least one of the CoPt film 201 and the CoPt film 203 and the CoPt film 202 can be collectively regarded as the free layer 4. Furthermore, at least one of the pinned layer composed of the CoPt films 201, 200 and the Ru film 76 and the pinned layer composed of the CoPt films 203, 205, 207 and the Ru films 204, 206 and the CoPt film 202 are combined. Can also be seen as the free layer 4.

On the Cu wiring 85, the reading structure 21 is provided. As the readout structure 21, a Ta film 91 having a thickness of 5 nm as an underlayer, a PtMn film 92 having a thickness of 20 nm as an antiferromagnetic material, a CoPt film 208 having a thickness of 2 nm as a magnetic material under the pinned layer, and pin layers A Ru film 94 having a film thickness of 0.8 nm, which is a conductor layer for antiferromagnetic coupling, a CoPt film 209 having a film thickness of 2 nm, which is a magnetic material on the pinned layer, and a MgO film 96 having a film thickness of 1 nm, which is the tunnel insulating layer 2. A NiFe film 97 having a thickness of 300 nm as the free layer 1 and a Ta film 98 having a thickness of 50 nm as the cap layer are laminated in this order. The read structure 21 is embedded in an SiO ₂ film 99 that is an interlayer insulating film. On the upper side of the readout structure 21, a Cu wiring (Cu upper electrode) 103 having a Ta film 102 as a barrier film embedded in an SiN film 100 and an SiO ₂ film 101 as interlayer insulating films is provided.

  However, the PtMn film 92 that is an antiferromagnetic material fixes at least the magnetization direction of the CoPt film 208 that is a pinned layer lower layer magnetic material. The CoPt film 208 of the pinned layer lower layer magnetic material and the CoPt film 209 of the pinned layer upper layer magnetic material constitute the magnetization fixed layer 3 that is antiferromagnetically coupled via the Ru film 94.

Next, a method for manufacturing the magnetoresistive memory element according to the first embodiment will be described with reference to FIG.
A Cu wiring (Cu lower electrode) 72 is formed on a part of the SiO ₂ film 70 which is an interlayer insulating film provided on a semiconductor substrate (not shown) on which transistors, wirings and the like are formed. And the upper part is planarized by the chemical mechanical polishing technique (Chemical Mechanical Polishing: hereinafter CMP). Thereafter, the Ta film 73 is 5 nm, the PtMn film 74 is 20 nm, the CoPt film 200 is 2 nm, the Ru film 76 is 0.8 nm, the CoPt film 201 is 2 nm, the CoPt film 202 is 50 nm, the CoPt film 203 is 2 nm, and the Ru film. 204 is 0.8 nm, CoPt film 205 is 4 nm, Ru film 206 is 0.8 nm, CoPt film 207 is 2 nm, PtMn film 79 is 20 nm, and Ta film 80 is 50 nm by sputtering. Subsequently, the Ta film 80 is processed by photolithography and RIE. After removing the resist by the ashing process, the PtMn film 79 to the Ta film 73 are processed into the shape of the writing structure 22 by the milling method using the Ta film 80 as a mask. Thereafter, an SiO ₂ film 81 having a thickness of 200 nm is formed on the entire surface by CVD, followed by planarization by CMP and exposing the Ta film 80.

Thereafter, an SiN film 82 is formed on the surface and an SiO ₂ film 83 is formed at 400 nm. Subsequently, a groove is formed in the SiO ₂ film 83 by photolithography and RIE, and the resist is removed by ashing. Next, the SiN film 82 in the trench is removed by RIE. Subsequently, after a Ta film 84 is formed on the entire surface, a Cu film 85 is grown by plating. Thereafter, the entire surface is subjected to CMP to form a Cu wiring 85 serving as an upper electrode of the write structure 22 only in the groove.

Next, on the entire surface, the Ta film 91 is 5 nm, the PtMn film 92 is 20 nm, the CoPt film 208 is 2 nm, the Ru film 94 is 0.8 nm, the CoPt film 209 is 2 nm, the MgO film 96 is 1 nm, the NiFe film 97 is 300 nm, Ta A film 98 is formed to a thickness of 50 nm by a sputtering method. Subsequently, the Ta film 98 is processed by photolithography and RIE. After removing the resist by the ashing process, the NiFe film 97 to the Ta film 91 are processed into the shape of the readout structure 21 by the milling method using the Ta film 98 as a mask. After that, an SiO ₂ film 99 is formed on the entire surface by 200 nm by the CVD method, and then planarized by CMP and the Ta film 98 is exposed. Then, a Cu wiring 103 serving as the upper electrode of the readout structure 21 is formed by the same process as described above.

  Thereafter, annealing is performed in a magnetic field perpendicular to the film surface of about 275 ° C., 2 hours, 1 T (Tesla), and the magnetization direction is fixed to the antiferromagnetic layer (74, 79, 92) for magnetization fixation. By exchange coupling the pinned layers (200/76/201, 207/206/205/204/203, 208/94/209), these pinned layers (200/76/201, 207/206/205 / 204/203, 208/94/209).

  The material of the second free layer (NiFe film 97) of the reading structure 21 is an in-plane magnetization film. However, by making the shape into a circle of 200 nmφ, the shape can be made long in the thickness direction. At this time, the magnetic body has an easy axis component in the direction perpendicular to the film surface due to shape anisotropy. It is assumed that the magnetization direction of each pinned layer is set as shown in FIG. The magnetization directions of the CoPt film 200, the CoPt film 207, and the CoPt film 208 that are pinned layers in contact with the PtMn films 74, 79, and 92 are fixed upward. The magnetization direction of the CoPt film 201 is fixed downward by setting the Ru film 76 to a film thickness that antiferromagnetically couples the upper and lower magnetic bodies. The magnetization direction of the CoPt film 203 is fixed upward by setting the Ru films 204 and 206 to a film thickness that antiferromagnetically couples the upper and lower magnetic bodies. At this time, since the lower surface portion of the CoPt film 202 is in contact with the CoPt film 201, the magnetization direction is fixed downward. On the other hand, since the upper surface portion of the CoPt film 202 is in contact with the CoPt film 203, the magnetization direction is fixed upward. In this embodiment, it can be seen that the CoPt film 201, the CoPt film 202, and the CoPt film 203 form the second free layer of the writing structure 22. Thus, the magnetization direction of the upper surface of the second free layer is fixed upward and the magnetization direction of the lower surface is fixed downward, so that a domain wall is always formed in the second free layer.

  Next, the data write operation of the MRAM of FIG. 6 using the magnetoresistive memory element as a memory cell will be described. First, the first transistor 52 and the second transistor 53 are turned on via the first word line 58 and the second word line 59 of the cell in which data is written by the word line control circuit 60. Further, a voltage is applied between the first bit line and the second bit line of the cell in which data is written by the bit line control circuit 57, and the domain wall in the second free layer of the write structure 50 (same as 22). A desired write current, for example 0.2 mA, sufficient to move the current is applied. When a write current is passed from the Cu wiring 85 to the Cu wiring 72, electrons flow from the region where the magnetization is fixed downward in the CoPt film 202, and the domain wall in the second free layer is moved upward. As a result, the magnetization direction of the CoPt film 202 changes downward. Further, when a write current is passed from the Cu wiring 72 to the Cu wiring 85, electrons flow from a region where the magnetization is fixed upward on the upper surface of the CoPt film 202, and move down the domain wall in the second free layer. Let As a result, the magnetization direction of the CoPt film 202 changes upward. The second free layer of the write structure 50 and the first free layer of the read structure 51 (same as 21) are magnetostatically coupled. Therefore, when the magnetization direction of the second free layer of the write structure 50 is set, the magnetization direction of the first free layer of the read structure 51 is also set. That is, the magnetization directions of the first free layer and the second free layer can be set according to the direction of the write current.

  Next, data reading from the MRAM in FIG. 6 using the magnetoresistive memory element as a memory cell will be described. First, the third transistor 54 of a cell to be read out via the lead wire 63 is turned on by the lead wire control circuit 64. Further, the first transistor 52 is turned on by the word line control circuit 60. Further, a read current, for example, 20 μA is applied from the bit line control circuit 57 to the first bit line 55 of the memory cell to be read. The read structure has a resistance value of 10 kΩ or 20 kΩ depending on the written data. As a result, when the ON resistance of the selected first transistor 52 and third transistor 54 connected to the magnetization fixed layer (3) is 1 kΩ, the potential of the first bit line 55 is 0.21V, 0. 41V is shown. Data can be discriminated by selecting the potential of the first bit line 55 by the select circuit 62 and applying it to the differential sense amplifier 65 and setting the reference potential Vref of the reference potential applying circuit to 0.3V.

  In the second embodiment, one electrode of the write structure 22 and one electrode of the read structure 21 are shared. Therefore, there are advantages that the number of manufacturing steps is reduced and the yield is improved.

  As described above, according to the present invention, since domain wall motion is used for data writing, writing with low current and low power is possible. Furthermore, since the data write current does not flow through the tunnel insulating film, the deterioration of the tunnel insulating film can be suppressed, and a highly reliable magnetoresistive memory device can be realized.

  The present invention is not limited to the above embodiments, and it is obvious that each embodiment and each embodiment can be appropriately changed within the scope of the technical idea of the present invention.

  A part or all of the above embodiments and examples may be described as in the following supplementary notes, but are not limited to the following.

(Supplementary note 1) A read structure and a write structure provided in the vicinity of the read structure, the read structure having a first free layer whose magnetization direction changes, and a magnetization direction fixed. The magnetization fixed layer, and a tunnel insulating layer provided between the first free layer and the magnetization fixed layer, and the write structure includes a second free layer whose magnetization direction changes, The second free layer is provided on an upper surface of the film of the second free layer, and is provided on a lower surface of the film, a first magnetization fixed region in which magnetization is fixed in a first direction, and a second direction. And a second magnetization fixed region whose magnetization direction is fixed, a domain wall exists in the film surface direction of the film, and the first free layer and the second free layer are magnetostatically coupled. Magnetoresistive memory element.

(Supplementary note 2) The magnetoresistive storage element according to supplementary note 1, wherein the read structure is disposed in a direction perpendicular to the film surface of the write structure.

(Supplementary note 3) The magnetoresistive storage element according to supplementary note 2, wherein the first direction and the second direction are substantially opposite to each other.

(Supplementary note 4) In the magnetoresistive storage element according to supplementary note 2 or 3, the write structure includes a third electrode electrically connected to the first magnetization fixed region, and the second magnetization fixed region. A fourth electrode electrically connected to the first electrode, and the movement of the domain wall moving in a direction perpendicular to the film surface by a current flowing between the third electrode and the fourth electrode. Magnetoresistive memory element that controls data to be written in the direction.

(Supplementary note 5) In the magnetoresistive storage element according to supplementary note 4, the read structure is electrically connected to the first electrode electrically connected to the first free layer and the magnetization fixed layer. A magnetoresistive storage element that further includes a second electrode, and reads out data by evaluating a characteristic value having a correlation with a resistance between the first electrode and the second electrode.

(Supplementary note 6) The magnetoresistive storage element according to any one of supplementary notes 2 to 5, wherein the first direction and the second direction substantially coincide with an easy axis direction of the second free layer. .

(Appendix 7) In the magnetoresistive memory element according to any one of appendices 2 to 6, the easy axis direction of the first free layer and the easy axis direction of the second free layer are substantially in the same direction. Magnetoresistive memory element.

(Appendix 8) In the magnetoresistive memory element according to any one of appendices 2 to 6, the easy axis direction of the first free layer and the easy axis direction of the second free layer are substantially orthogonal to each other. Magnetoresistive memory element.

(Supplementary note 9) In the magnetoresistive storage element according to any one of supplementary notes 2 to 8, the write structure is adjacent to at least one of the first magnetization fixed region and the second magnetization fixed region. A magnetoresistive memory element further provided with a magnetization fixing unit that is provided and fixes the magnetization direction of the adjacent portion.

(Supplementary note 10) The magnetoresistive storage element according to supplementary note 9, wherein the magnetization fixed portion is an antiferromagnetic material.

(Supplementary note 11) In the magnetoresistive memory element according to supplementary note 9, the magnetization fixed portion is a stacked body, and the stacked body is between a plurality of magnetic bodies whose magnetization directions are fixed and the plurality of magnetic bodies. And at least one non-magnetic material that antiferromagnetically couples the magnetic materials laminated on both sides.

(Supplementary note 12) In the magnetoresistive memory element according to supplementary note 9, the magnetization fixed portion is a stacked body, and the stacked body is provided between a plurality of magnetic bodies whose magnetization directions are fixed and the plurality of magnetic bodies. And at least one non-magnetic material that ferromagnetically couples magnetic materials laminated on both sides.

(Supplementary note 13) In the magnetoresistive memory element according to supplementary note 9, the magnetization fixed portion is a stacked body, and the stacked body is provided between a plurality of magnetic bodies having a fixed magnetization direction and the plurality of magnetic bodies. And at least one non-magnetic material that antiferromagnetically couples the magnetic materials laminated on both surfaces, and the number of the first magnetization fixed regions and the number of the second magnetization fixed regions stacked. A magnetoresistive memory element that differs from the number of bodies by an odd number.

(Supplementary note 14) The magnetoresistive storage element according to supplementary note 5, wherein the second electrode and the third electrode are electrically connected.

(Supplementary Note 15) A plurality of magnetoresistive memory elements and a peripheral circuit that drives the plurality of magnetoresistive memory elements, each of the plurality of magnetoresistive memory elements is as described in any one of Supplementary Notes 1 to 14. A magnetic random access memory which is a magnetoresistive storage element described.

(Supplementary note 16) The magnetic random access memory according to supplementary note 15, wherein a part of the magnetoresistive storage element and the peripheral circuit are formed on different substrates and attached to each other.

(Supplementary note 17) The magnetic random access memory according to supplementary note 16, wherein the read structure and the write structure are formed on different substrates.

DESCRIPTION OF SYMBOLS 1 1st free layer 2 Tunnel insulating layer 3 Pin layer 4 2nd free layer 5 1st electrode 6 2nd electrode 7 3rd electrode 8 4th electrode 9 1st magnetization fixed area | region 10 2nd Magnetization fixed region 11 Domain wall moving region 21 Read structure 22 Write structure 40 MRAM
41 memory cell array 55 first bit line 56 second bit line 57 bit line control circuit 58 first word line 59 second word line 60 word line control circuit 61 data line 62 select circuit 63 read line 64 read line control circuit 65 Differential Sense Amplifier 66 Reference Potential Application Circuit

Claims (9)

A readout structure;
A write structure provided in the vicinity of the read structure,
The readout structure is
A first free layer whose magnetization direction changes;
A magnetization fixed layer with a fixed magnetization direction;
A tunnel insulating layer provided between the first free layer and the magnetization fixed layer in the film thickness direction of both the first free layer and the magnetization fixed layer;
The writing structure is:
Comprising a second free layer whose magnetization direction changes;
The second free layer is
A first magnetization fixed region provided on an upper surface of the film of the second free layer and having magnetization fixed in a first direction;
A second magnetization fixed region provided on a lower surface of the film and having a magnetization direction fixed in a second direction,
There is a domain wall in the film surface direction of the film,
The read structure is disposed in a direction perpendicular to the film surface of the write structure such that the first free layer or the magnetization fixed layer is opposed to the first magnetization fixed region of the write structure. Has been
A magnetoresistive memory element, wherein the first free layer and the second free layer are magnetostatically coupled. The magnetoresistive memory element according to claim 1.
The magnetoresistive memory element, wherein the first direction and the second direction are substantially opposite to each other. The magnetoresistive memory element according to claim 1 or 2,
The writing structure is:
A third electrode electrically connected to the first magnetization fixed region;
And a fourth electrode electrically connected to the second magnetization fixed region,
A magnetoresistive memory element that controls data to be written in the direction of movement of the domain wall that moves in a direction perpendicular to the film surface by a current flowing between the third electrode and the fourth electrode. The magnetoresistive memory element according to claim 3,
The read structure is
A first electrode electrically connected to the first free layer;
A second electrode electrically connected to the magnetization fixed layer,
A magnetoresistive memory element that reads out data by evaluating a characteristic value having a correlation with a resistance between the first electrode and the second electrode. The magnetoresistive memory element according to any one of claims 1 to 4,
The magnetoresistive memory element, wherein the first direction and the second direction substantially coincide with an easy axis direction of the second free layer. The magnetoresistive memory element according to any one of claims 1 to 5,
The magnetoresistive memory element, wherein an easy axis direction of the first free layer and an easy axis direction of the second free layer are substantially the same direction. The magnetoresistive memory element according to any one of claims 1 to 5,
The magnetoresistive memory element, wherein an easy axis direction of the first free layer and an easy axis direction of the second free layer are substantially orthogonal to each other. The magnetoresistive memory element according to any one of claims 1 to 7,
The write structure is further provided with a magnetization fixed portion that is provided adjacent to at least one of the first magnetization fixed region and the second magnetization fixed region and fixes the magnetization direction of the adjacent portion. element. A plurality of magnetoresistive memory elements;
A peripheral circuit for driving the plurality of magnetoresistive storage elements,
Each of the plurality of magnetoresistive memory elements is the magnetoresistive memory element according to any one of claims 1 to 8. Magnetic random access memory.

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